1. Field of the Invention:
The present invention relates to the preparation of N,N'-bis(2-hydroxyethyl)oxamide by reacting ethanolamine with an alkyl oxalate in an aqueous reaction medium.
2. Description of the Prior Art:
N,N'-Bis(2-hydroxyethyl)oxamide is a known compound which is useful, e.g., as an intermediate in the manufacture of powerful explosives [cf. M. G. Desseigne, Revue des Poudres, 30, page 101 (1948) and R. S. Stuart et al, Can. J. Res., 26, page 402 (1948)]. N,N'-Bis(2-hydroxyethyl)oxamide is typically prepared by condensing ethanolamine with a dialkyl oxalate. Since publication in L. Knorr and P. Rossler, Ber., 36, pages 1278-1279 (1903) this condensation has been carried out in an anhydrous reaction medium, either in the absence of solvent or employing an excess of ethanolamine, or in anhydrous alcohol; cf. A. P. Phillips et al, J. Am. Chem. Soc., 73, page 5557 (1951), G. F. D'Alelio et al, J. Am. Chem. Soc., 59, page 111 (1937), R. S. Stuart et al, loc. cit., and M. G. Desseigne, loc. cit. These latter authors have emphasized the need to employ anhydrous solvents as reaction media, in particular alcohols such as ethanol and butanol. Best yields of N,N'bis(2-hydroxyethyl)oxamide are obtained when alcohols are employed as solvents. In this case, yields based on oxalate or ethanolamine exceed 90% and can be quantitative. In spite of the immediately aforesaid, such processes suffer from two major disadvantages which make them impracticable on an industrial level. The first of these disadvantages relates to the productivity of the reaction, which is found to be particularly low and on the order of 110 kg/m.sup.3 of reaction medium, in the best of cases. Furthermore, it has also been found that, when an alcohol is used as the reaction solvent, the N,N'-bis(2-hydroxyethyl)oxamide precipitates as it is being produced in the form of finely divided, alcohol-swollen particles, which results in the formation of a non-fluid cream which adheres to the reactor walls. This cream is quite difficult to remove from the reaction apparatus and to filter off. Preparation of N,N'-bis(2-hydroxyethyl)oxamide on an industrial scale consequently has entailed the use of a reaction medium as free as possible from the aforementioned disadvantages but which nevertheless provides good yields.